Remove use of strnlen on Mac OS, because pre-Lion versions don't have it.

runtime/bin/directory_macos.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "bin/directory.h"
 
 #include <dirent.h>
 #include <errno.h>
 #include <string.h>
 #include <sys/param.h>
@@ skipping 11 matching lines @@
 
   char data[PATH_MAX + 1];
   int length;
 
   bool Add(const char* name) {
     size_t written = snprintf(data + length,
                               PATH_MAX - length,
                               "%s",
                               name);
     data[PATH_MAX] = '\0';
-    if (written == strnlen(name, PATH_MAX + 1)) {
+    if (written == strlen(name)) {
       length += written;
       return true;
     } else {
       errno = ENAMETOOLONG;
       return false;
     }
   }
 
   void Reset(int new_length) {
     length = new_length;
@@ skipping 19 matching lines @@
 static PathBuffer* ComputeFullPath(const char* dir_name) {
   PathBuffer* path = new PathBuffer();
   char* abs_path;
   do {
     abs_path = realpath(dir_name, path->data);
   } while (abs_path == NULL && errno == EINTR);
   if (abs_path == NULL) {
     delete path;
     return NULL;
   }
-  path->length = strnlen(path->data, PATH_MAX);
+  path->length = strlen(path->data);
   if (path->Add(File::PathSeparator())) {
     return path;
   } else {
     delete path;
     return NULL;
   }
 }
 
 static bool HandleDir(char* dir_name,
                       PathBuffer* path,
@@ skipping 294 matching lines @@
     return NULL;
   }
   char* result;
   do {
     result = mkdtemp(path->data);
   } while (result == NULL && errno == EINTR);
   if (result == NULL) {
     delete path;
     return NULL;
   }
-  int length = strnlen(path->data, PATH_MAX);
+  int length = strlen(path->data);
   result = static_cast<char*>(malloc(length + 1));
   strncpy(result, path->data, length);
   result[length] = '\0';
   delete path;
   return result;
 }
 
 
 bool Directory::Delete(const char* dir_name, bool recursive) {
   if (!recursive) {
     return (TEMP_FAILURE_RETRY(remove(dir_name)) == 0);
   } else {
     return DeleteRecursively(dir_name);
   }
 }
 
 
 bool Directory::Rename(const char* path, const char* new_path) {
   ExistsResult exists = Exists(path);
   if (exists != EXISTS) return false;
   return (TEMP_FAILURE_RETRY(rename(path, new_path)) == 0);
 }